1. Field of the Invention
The present invention relates to a range finding device of scanning type used for a system of alerting collisions of a vehicle.
2. Discussion of Background
An example of a conventional range finding device of a scanning type is disclosed in, JP-A-7-84045. In this reference, a range finding device for emitting laser beams in a plurality of directions and receiving reflected light from objects, respectively positioned in emitting directions of the laser beams, in order to respectively measure ranges is disclosed. The device simultaneously scans the plurality of laser beams for measuring the ranges from the objects, respectively positioned in the directions of emitting the laser beams. According to this device, a scanning period is shortened to be one of the number of the plurality of the laser beams and a degree of freedom is increased in designing an optical system.
However, such conventional range finding techniques have problems. For example, a plurality of laser diodes are necessary and thereby the cost is increased.